I noticed that too. My BMS turns off if it's just hooked up but not actively charging or discharging regularly. I had intended to mess with settings to get this behavior to either stop or extend beyond the 1 or 2 days I see right now. BTW...0 typically means off. If you are wanting week long on periods, then 999 ought to accomplish that, but I think if you want the sleep function disabled, that's probably 0.

9999 does not work, came back after 8 hours and BT was off. 999 is only 16 hours. will mess around but 0 did not turn it off.
i will email them and ask if they can add the option.

Hey Circuit...
I have an idea for you. Your BMS is an all in one device. How about split out the power mosfets to a separate board and then make the balancing and monitoring boards stack-able. This allows your product to reach a far broader market (people like me!!!) where 16S is flat out a show stopper. The larger my pack is, the more it costs and the more I'm willing to pay for battery protection. At 16S, IMHO, I'm going to go with whatever is cheap for no other reason than the battery pack cost is not that great. IE: It's NOT compelling to spend a lot of money on a BMS that costs almost as much as my batteries do. With a stack-able board option and separate mosfet board, you can build 16S BMS all you want and then expand it to a 32S option that works at 20-32S. Add a third balance board and now you've reached 95% of the DIY market and probably a lot of the high end commercial builders too! The mosfet board can then be built in several options...such as 50, 100, 200, 300 amps. And of course build them to voltage requirements. The Chinese do this all day long. Why can't Western world BMS makers figure this out and then do it for a reasonable price?

Modular balance section, from 3s to 112s, mentions Bluetooth, separate power board. Not enough detail on the product listing page though. I'll contact the seller and probably order what appears to be the basic needed modules.

This is somewhat common. I've been caught by this too. A few years ago I bought what I was told was a full production run smart BMS. What I got looked like prototypes that had been hacked together. They had quite a few places where obvious rework had been done to them to fix bugs in the BMS. One BMS was DOA and another randomly would not see all of the cells attached to it. They were supposed to be BT and USB capable. BT never worked and the phone app would crash constantly. The PC app was slightly better, but again crashed all the time and if it did stay running would NOT program the BMS half the time. In the end I discovered that the manufacturer had made 3 prototype BMS and I had all of them and that they had never actually done a production run at all. Grrrr! I of course demanded a full refund. They do this to see if there is interest in a new product. If there is, then they take the vaporware product and start a real production run.

This is somewhat common. I've been caught by this too. A few years ago I bought what I was told was a full production run smart BMS. What I got looked like prototypes that had been hacked together. They had quite a few places where obvious rework had been done to them to fix bugs in the BMS. One BMS was DOA and another randomly would not see all of the cells attached to it. They were supposed to be BT and USB capable. BT never worked and the phone app would crash constantly. The PC app was slightly better, but again crashed all the time and if it did stay running would NOT program the BMS half the time. In the end I discovered that the manufacturer had made 3 prototype BMS and I had all of them and that they had never actually done a production run at all. Grrrr! I of course demanded a full refund. They do this to see if there is interest in a new product. If there is, then they take the vaporware product and start a real production run.

The first one you link does look a bit hacked together. The second one I have asked for more info on and have been promised the documentation. We shall see if it shows up and is worth a risk.

It's just funny that we were talking about modular systems and all of the sudden I come across no less than 4-6 different ones in that particular store. So skepticism has kept me from actually ordering them. I do need to order one of the 8-24S and 16-32S units though as those have proven somewhat decent it seems. I would like one that will go as low as 3-4 though. Perhaps if I can order it a single unit of the 2nd one is worth a risk.

This is somewhat common. I've been caught by this too. A few years ago I bought what I was told was a full production run smart BMS. What I got looked like prototypes that had been hacked together. They had quite a few places where obvious rework had been done to them to fix bugs in the BMS. One BMS was DOA and another randomly would not see all of the cells attached to it. They were supposed to be BT and USB capable. BT never worked and the phone app would crash constantly. The PC app was slightly better, but again crashed all the time and if it did stay running would NOT program the BMS half the time. In the end I discovered that the manufacturer had made 3 prototype BMS and I had all of them and that they had never actually done a production run at all. Grrrr! I of course demanded a full refund. They do this to see if there is interest in a new product. If there is, then they take the vaporware product and start a real production run.

The first one you link does look a bit hacked together. The second one I have asked for more info on and have been promised the documentation. We shall see if it shows up and is worth a risk.

It's just funny that we were talking about modular systems and all of the sudden I come across no less than 4-6 different ones in that particular store. So skepticism has kept me from actually ordering them. I do need to order one of the 8-24S and 16-32S units though as those have proven somewhat decent it seems. I would like one that will go as low as 3-4 though. Perhaps if I can order it a single unit of the 2nd one is worth a risk.

They are both available.
I ordered one with 11s balance modules up to over 100s. Canceled by seller.
The first one you listed is no advantage over the 24s by model.
The second seems bulky and expensive. Nice balance function though.

If you want to keep the bms from cutting out the bluetooth you can, The bluetooth dies when there is no current flow. On itself that is fine for most people but i would like to see the bms settings when it is done charging the next morning without having to turn on the controller to wake it up again.
Right now i tried setting the sleep timer to 9999 and see if it sticks. That should be 7 days before it sleeps.

I noticed that too. My BMS turns off if it's just hooked up but not actively charging or discharging regularly. I had intended to mess with settings to get this behavior to either stop or extend beyond the 1 or 2 days I see right now. BTW...0 typically means off. If you are wanting week long on periods, then 999 ought to accomplish that, but I think if you want the sleep function disabled, that's probably 0.

i WISH this was the case with my BMS. i can't make it shut down properly. it balances really nicely, but it NEVER seems to shut down completely. this is the second one i have so i can exclude a hardware error. it seems this is a software bug.
voltage drops measureable even with my 10p pack - 30Ah. 17mV over 3 days. that may not seem a lot, but that's 150mA per month. if you store a depleted pack that could be damaged quite easily.

this bms has a actual "off". at that point all the leds are off and it's basically dead. dont know the power comsumption at that point yet but on the other hand: these are S20+ BMS, not meant for dinky little packs and if you put a discharged pack away for months at a time it's kinda on you. its not that hard to simply put it at 3.6v and disconnect the -B line or remove the balance connectors (that remoces the + line for the bms power) for long term storage. a battery pack is a expensive thing, you need to take care of it if you want it to last.

flippy, a drop of 0,15V in one month on a battery which has 30A is definitely not normal.
Think about a normal e-bike battery which have more like 10Ah. Such battery would be dead if stored over the winter month even if fully charged (0,45V per month).

When i stored one 48V 12Ah battery over the winter, it was about half charged and the Led indicator did show same SOC after 4 month.

its not that hard to simply put it at 3.6v and disconnect the -B line or remove the balance connectors (that remoces the + line for the bms power) for long term storage. a battery pack is a expensive thing, you need to take care of it if you want it to last.

i will NOT remove power leads and stuff from my battery if i put it away for a month or so - and a month can be enough to deep discharge the battery.
a BMS is there to SAVE the battery. if it discharges the battery (after balancing is done) then it's a WRONG DESIGN. i have a "non BT style" BMS connected to my lifepo4 pack for over a year now, w/o touching the battery and it hasn't changed the SOC a single bit.

This is truly confounding! This is a 32S BMS. That means it realistically needs to handle upwards of 140 volts depending on cell chemistry. So why does it have 100 volt mosfets (HY45N10's) on the C- side? Why no access to P- where it has 150 volt IRF4115's? There is no part of 100 volt mosfets that are OK in a 32S BMS designed for 140 volt continuous operation. I can't imagine what the manufacturer was thinking!

if you look further back you can see that the C- mosfets are different and not rated for the voltage unlike the B- side.

Yes the thing with those 100V FET's is indeed confusing, but if you think hard about it there should not be a problem, because the maximum voltage those C- FET's should ever see is just the voltage difference between a full and empty battery (if the charger gets connected).
Thats the way it works and i don't think the manufacturer would make such big mistake.

In case of 32S LiIon it would mean about 135V (when fully charged) minus 64V (2V per cell) if the battery is completely discharged which makes a difference of 71V and this is below the rating.

There is still the question why they were using the 100V HY045N10 instead of the IRF4115 ?

-> for lowering the losses!

The HY have 4,5 mOhm Rds while the IRF with it's 9,3 mOhm have more than twice the resistance.
So the C- FET's will produce less than half of the heat as the P- FET's do.
Or with other words: if you attach the load to C- (like described), than the accruing heat losses will be only about 50% more instead of attaching it between the two groups.

Still...I want mosfets that can handle the full voltage that the BMS could possibly see. Not that I care over much really. I won't be using the C- mosfets anyway. Honestly, I go with the best mosfets I can get and at 150 volts that's the AOT2500. More than likely, when I get to use these BMS, the factory mosfets will get pulled and replaced. This will also make the BMS capable of much more than 300 amps and at significantly less heat than any other 150 volt mosfet option. Mu guess is that at 131 volts I'll be pulling something like 120 amps at least and more is possible.

I still have these 2 Smart BMS units lying around. I am glad to see much more information on them. I had a good feeling they were decent units.

I am still having the same issue with the BMS, the unit will beeping rapidly shortly after turning it on. Charge or Discharge will not work. The translation for the error on screen states MOS tube closed.

You have the 24s <100V BMS, right? so it would be really stupid to swap them out for AOT2500 which have more than twice the resistance.
The HY's are not bad. Almost as good as the widley used IRF4110 in terms of Rds on

How do I check if the fets are broken?

It is simple you just need to set a multimeter to continuity test mode (where it beeps) and measure between B- and P- (the row beteween the two groups of FETs) and between P- and C-. If it beeps, than one or more FET's of this group have a short and are dead. To find the brokden one, you would need to desolder all and measure them individual.
Make sure the BMS is not attached to the battery.

You have the 24s <100V BMS, right? so it would be really stupid to swap them out for AOT2500 which have more than twice the resistance.
The HY's are not bad. Almost as good as the widley used IRF4110 in terms of Rds on

How do I check if the fets are broken?

It is simple you just need to set a multimeter to continuity test mode (where it beeps) and measure between B- and P- (the row beteween the two groups of FETs) and between P- and C-. If it beeps, than one or more FET's of this group have a short and are dead. To find the brokden one, you would need to desolder all and measure them individual.
Make sure the BMS is not attached to the battery.

If you realistically want the BMS to support 150 volts, then yes, 100 volt mosfets are not the right answer. BUT, will they likely ever see more than 100 volts? No not really. On C- 100 volt mosfets are OK...ish. Assuming getting down to 2.5 volts per cell at 32S which is probably the largest voltage difference the mosfets are ever likely to see. That's 80 volts. At fully charged at 4.1 volts per cell, that's 131.5 volts or a difference of 51.5 volts. This is what those 100 volt 45N10 mosfets are likely to ever see so it's probably OK for them to not be 150 volt parts. The 45N10 does have half the RDS of the AOT2500 and similar current capabilities. Of course you are leg limited to 75 amps so 150 amps or 164 amps is irrelevant. However, I'd still power the EV at P- and use C- only for charging.

Chinese made BMS...extremely high chance that these are Chinese mosfets...AKA NOT as good as the legit part. I have some IRF4110's that I bought from Digikey and some that came from a Chinese seller. I can tell you they are NOT the same grade of part. Lots of mosfets are similar enough in specs that if you get a small sample, you would NOT know 2 parts were different. They could fit within the specs for any number of similar parts. Then it comes down to laser etching whatever part number you want on the package. AKA a 34n10 can be an irf4110 can be an 85n10 and so on. Good mosfets from legit sources cost more for good reasons.

You can see this quite literally in LED's. Get a real CREE XML and one from a Chinese seller. Power both at the exact same factory spec'd voltage (3 volts I think). I bet the CREE part will be brighter, run cooler and draw less current than the Chinese part. Turn the voltage up gradually on each LED until they burn out. The Chinese LED will take maybe an extra .2 or .3 volts while the CREE will take 1-2 volts more. You do get what you pay for! I did this test not so long ago on a Chinese XHP70 and a real CREE XHP70. They are 6 volt LED's. Power them up and the CREE is blindingly bright and the light is yellowish (on the BIN i bought). The Chinese LED was still bright, but probably 70-80% as bright, drew more current, ran hotter and was very bluish (6700K or so). I then added .2 volts, that got both LEDs a good bit brighter, but the Chinese LED within a 20 seconds was getting hotter. I then bumped to 6.4 volts. The Chinese LED was rapidly having serious issues and a minute later was at maybe 50% brightness (burned out). The CREE on the other hand suffered no loss of brightness many hours later despite being ran at 7 volts continuous. THat's legit parts vs Chinese parts for you!

China is great for cheap stuff, but it also means you may not be getting legit parts either. They have no copy right laws there and anybody can make and sell fakes with no consequences to them...buyer beware! Depending on the factory mosfets for the maximum current they supposedly can handle is possible, but can you keep them there for very long? I'm not entirely sure you can.

Did you read the whole thread? If so you may have noticed that i discovered and tested the K1 connector which serves as an on/off switch.
Still, the BMS draws way too much power in power off state. It was off for a week now and voltage of my 15s10p 30q cells dropped by 20mV. That's a magnitude of self discharge.
I wish there was way to get the source code of the cpu. This would ebable us to tune the code and make it a real excellent BMS.

@flippy: afair you have a different version BMS than i have. 15s and 20s are not the same type.
there may be different programming inside.
but still i'd be interested in long term voltage drop of any BMS here. maybe you guys could tell us how much voltage drops within a week. if you ever don't use your bike for that long

@flippy: afair you have a different version BMS than i have. 15s and 20s are not the same type.
there may be different programming inside.
but still i'd be interested in long term voltage drop of any BMS here. maybe you guys could tell us how much voltage drops within a week. if you ever don't use your bike for that long

i think these BMS's are all the same. the control board and software are identical. its a very modular design and they try and fit the same design and software for virutally all applications they can find.
there might be slight tweaks but the general control and firmware will be the same. that probably means they all have the same issues.
power consumption can be different depending on the board design but i doubt there will be much of a difference.

Are you sure?
The software looks different (at least from the pics), and the circuit boards as well.

btw:
I own the 13s 30A version which is, aside from two solder joints, identical to the 15s version. The junctions are between input 8-9 and 13-14 (see pic).

I have not as yet wired it up, but i could imagine that if the BT module is permanently attached that it drains more current as if it's not, but thats only a guess.
If there really is a problem with too high current draw even if the BT module is disconnected and on top of that if it's even turned off with the optional on/off switch, than these BMS's are garbage!

as i said, there are slight differences but they all display the same program on their identical lcd panels (if you opt for that) and they use the same android app. that means they run basically the same software and have the same control cpu.

I have this smart BMS, https://www.aliexpress.com/item/8S-60A- ... 70262.html
I installed the K1 switch, and enabled it. for me it only controls the discharge fets, on/off, everything else continues to tick along in the background.
I have not hacked into the code of the chips, but the SW protocol, and can read and write to the BMS with my arduino.https://github.com/bres55/Smart-BMS-arduino-Reader
Thought I'd share it, someone might find it useful.
I am thinking later on to use the balance signals from the BMS, to switch on/off some low power fans across each set of cells to get a larger balance current. That way I am using the BMS algorithm, to balance, and no hardware tampering. But will see how it goes with the 30mA first.